Known in the art is a method of forming a signal in a fire alarm unit, connected with its output to a communication line with a receiving-monitoring instrument, which comprises a monitored fire factor detector and a transmitting device connected to the output of the alarm unit, said method consisting in detecting an excess of the threshold value of the monitored fire factor, generating an alarm signal and transmitting this alarm signal to the communication line with the aid of a transmitting device (IVS-Signalspetsavtomatika products catalogue, Obninsk, 2000, page 2 “IP212-44 (DIP-44) Optical-electronic fire smoke alarm unit”).
The known method of transmitting information is simple to implement, but it lacks testing of the operability of the alarm unit components and of the dust content of the optical chamber, thereby the operational reliability of the method being lowered.
Closest in the technical essence and attainable result to the present method is a method of forming and transmitting signals from a fire alarm unit to a receiving-monitoring instrument via a communication line with the aid of a transmitting device which forms part of the alarm unit, which method comprises self-testing of the operability of the alarm unit components and measuring the value of a monitored fire factor (www.systemsensor.ru). The formation and transmission of the value of the monitored fire factor and of the failure information via the communication line are performed in a digital code with the aid of a receiving-transmitting device.
The disadvantages of the known method of forming a signal in a fire alarm unit are as follows: high prime cost of the process due to the use of an expensive alarm unit and an expensive receiving-monitoring instrument, which comprise devices for digital exchange of information, as well as low reliability and noise immunity of the digital link of the instrument with the alarm unit, and limitations as to the compatibility of instruments and alarm units (digital information exchange protocols being individual for each type of instrument and alarm unit).